Reduced wire profile stent

ABSTRACT

Methods and apparatuses of stents with likely reduced rates of tissue perforation are provided. Some embodiments include reducing the profile of a portion of the stent using a wire profile reduction electropolishing bath and/or other wire profile reduction means.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/644,255, filed Oct. 3, 2012, which claims the benefit of U.S.Provisional Application No. 61/543,166, filed on Oct. 4, 2011, thedisclosures of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to medical devices and more specifically,stents.

BACKGROUND

Stents are medical devices commonly used to maintain patency of bodyvessels, such as those of the vascular and gastrointestinal systems.Stents are often delivered via a minimally invasive procedure andthereafter expanded to contact and support the inner wall of thetargeted vessel. In general, most stents include a tubular shapedsupport structure having a plurality of interstices configured tofacilitate compression and expansion of the stent.

Many stents include proximal and distal flanges or flared ends toprevent stent migration subsequent to implantation. Flanges or flaresare typically set to a larger expanded diameter relative to the stentcentral portion and may exert a higher radial force per unit areaagainst the vessel wall, thereby securing the stent in position. Oneproblem with these features, however, is that the flanges or flares candamage the vessel wall if they are excessively rigid. Specifically, thecrowns at the end of a flange or flare can cause perforations as theluminal wall engages the stent during peristalsis. The resulting tissueperforations may be painful and can lead to more serious complicationsincluding infection, hemorrhage, and possibly death.

BRIEF SUMMARY

In a first aspect, a stent is provided, including a wire configured intoa tubular body including a proximal tube portion, a distal tube portion,a central tube portion disposed between the proximal tube portion andthe distal tube portion, and a lumen extending between the proximal tubeportion and the distal tube portion; wherein the wire includes a firstprofile and a second profile, wherein the second profile is differentfrom the first profile.

In a second aspect, a method of manufacturing a reduced wire profilestent is provided, including bathing a first portion of a wire stent ina first wire profile reduction solution; and applying a firstelectropolishing voltage to the first wire profile reduction solutionbath to reduce the profile of the first portion of the wire stent.

In a third aspect, a method of manufacturing a changed profile wirestent is provided, including subjecting a first portion of a wire stentto a wire profile reduction means to change the profile of the firstportion of the wire stent.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The embodiments will be further described in connection with theattached drawing figures. It is intended that the drawings included as apart of this specification be illustrative of the exemplary embodimentsand should in no way be considered as a limitation on the scope of theinvention. Indeed, the present disclosure specifically contemplatesother embodiments not illustrated but intended to be included in theclaims. Moreover, it is understood that the figures are not necessarilydrawn to scale.

FIG. 1 illustrates a side view of an exemplary reduced wire diameterstent;

FIG. 1A illustrates a side view of an exemplary wire crown prior to wirediameter reduction;

FIG. 1B illustrates a side view of an exemplary wire crown after wirediameter reduction at the view 1B illustrated in FIG. 1;

FIG. 1C illustrates a front cross-sectional view of an exemplaryproximal end of a stent prior to wire profile reduction;

FIG. 1D illustrates a front cross-sectional view of an exemplaryproximal end of the exemplary stent illustrated in FIG. 1 after wirediameter reduction;

FIG. 2 illustrates a side view of an exemplary reduced wire diameterstent;

FIG. 2A illustrates a side view of an exemplary stent wire prior to wirediameter reduction;

FIG. 2B illustrates a side view of the exemplary stent wire after wirediameter reduction at the view 2B illustrated in FIG. 2;

FIG. 2C illustrates a side view of an alternate stent wire after wirediameter reduction;

FIG. 3 illustrates a side view of an exemplary reduced wire diameterstent;

FIG. 4 illustrates a side view of an exemplary reduced wire diameterstent;

FIG. 5 illustrates an exemplary method of manufacturing a reduced wirediameter stent; and

FIG. 6 illustrates an exemplary method of manufacturing a reduced wirediameter stent.

DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS

The exemplary embodiments illustrated provide the discovery of methodsand apparatuses for manufacturing stents which may have reduced rates oftissue perforation achieved by various apparatuses and methods,including but not limited to, reducing the wire profile of one or moreportions of the stent such as by subjecting it to a wire profilereduction electropolishing bath and/or other wire profile reductionmeans.

The present invention is not limited to those embodiments describedherein, but rather, the disclosure includes all equivalents includingthose of different shapes, sizes, and configurations, including but notlimited to, other types of stents. The devices and methods may be usedin any field benefiting from a stent. Additionally, the devices andmethods are not limited to being used with human beings, others arecontemplated, including but not limited to, animals.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art. In case of conflict, the present document, includingdefinitions, will control. Preferred methods and materials are describedbelow, although apparatuses, methods, and materials similar orequivalent to those described herein can be used in practice or testing.All publications, patent applications, patents and other referencesmentioned herein are incorporated by reference in their entirety. Thematerials, methods, and examples disclosed herein are illustrative onlyand not intended to be limiting.

The terms “comprise(s),” “include(s),” “having,” “has,” “can,”“contain(s),” and variants thereof, as used herein, are intended to beopen-ended transitional phrases, terms, or words that do not precludethe possibility of additional acts or structures. The present disclosurealso contemplates other embodiments “comprising,” “consisting of” and“consisting essentially of,” the embodiments or elements presentedherein, whether explicitly set forth or not.

The term “proximal,” as used herein, refers to a direction that isgenerally towards a physician during a medical procedure.

The term “distal,” as used herein, refers to a direction that isgenerally towards a target site within a patient's anatomy during amedical procedure.

The term “biocompatible,” as used herein, refers to a material that issubstantially non-toxic in the in vivo environment of its intended use,and that is not substantially rejected by the patient's physiologicalsystem. A biocompatible structure or material, when introduced into amajority of patients, will not cause an undesirably adverse, long-livedor escalating biological reaction or response. Such a response isdistinguished from a mild, transient inflammation which typicallyaccompanies surgery or implantation of foreign objects into a livingorganism.

A more detailed description of the embodiments will now be given withreference to FIGS. 1-6. Throughout the disclosure, like referencenumerals and letters refer to like elements. The present disclosure isnot limited to the embodiments illustrated; to the contrary, the presentdisclosure specifically contemplates other embodiments not illustratedbut intended to be included in the claims.

When in a body, stents are often subjected to tortuous conditions,especially in bodily areas wherein peristaltic motion is present or whenthe stent is subjected to a curved orientation, such as when disposedwithin the colon or duodenum. When in such a position, the radial forceexerted by the stent onto the surrounding tissue may cause such tissueto perforate, thereby injuring or causing death to the patient. Oneadvantage from the embodiments disclosed herein and equivalents theretois that the stent is able to better conform to the tissue and is betterable to adapt to the tissue environment while maintaining good radialforce to maintain an open pathway. Another advantage includes, but isnot limited to, that the embodiments may aid in the reduction ofhyperplasia in that the radial force exerted from the stent may betailored to the surrounding tissue. Such benefits and other benefits areachievable through various apparatuses and methods described herein andequivalents thereto.

For example, FIG. 1 illustrates a side view of exemplary reduced wirediameter stent 100 having proximal portion 100 a, distal portion 100 b,and a generally cylindrical tubular shaped stent body 102 having lumen104 extending throughout. Stent 100 is preferably made from a shapememory alloy, such as nitinol, although other materials arecontemplated, including but not limited to FeMnSi and FeNiCo(Al,Ti)Tawith or without B, Fe₃Pt.

At proximal portion 100 a and distal portion 100 b of stent 100 areflanges 105 terminating in crowns 103. Stent 100 comprises a single wirewound in a helical pattern forming a cylindrical tubular shape; otherembodiments of wire stents are contemplated, including but not limitedto, those fabricated from two or more wires having helical or otherconfigurations. After stent 100 is fabricated, the diameter of wirefirst portion 106 is reduced by about 50% (other amounts arecontemplated) thereby making proximal portion 100 a and distal portion100 b of stent 100 more flexible and less traumatic to tissue, and thus,less likely to perforate tissue.

FIG. 1A illustrates a side view of exemplary wire crown 103 a prior towire diameter reduction, and FIG. 1B illustrates a side view ofexemplary wire crown 103 after wire diameter reduction at the view 1Billustrated in FIG. 1. As is illustrated in FIG. 1A, the diameter ofstent wire at crown portion 103 a prior to having the wire diameterreduced is 50% larger than is reduced wire crown portion 103 illustratedin FIG. 1B. Accordingly, force F1 (illustrated in FIG. 1A) exerted fromthe stent prior to wire diameter reduction is greater than force F2(illustrated in FIG. 1B) exerted after wire diameter reduction.

The flexural stiffness (K) of a component is generally defined by:

${{EI}\frac{y}{x}} = {{\int_{0}^{x}{{M(x)}\ {x}}} + C_{1}}$

(hereafter, “Equation 1”), where E=materials Young's modulus (Pascal);I=second moment of inertia (m⁴); y=transverse displacement of a beam atx; and M(x)=bending moment at x. The flexural stiffness has SI units ofPa. m⁴. As further explained herein, a wire beam may have any profileshape and is not limited to having a circular cross-sectional profile.However, for explanatory purposes, a circular cross-sectional profilewill be considered only for these next equations. Also assumed only forthese next equations is that the materials are constant such that thestent is fabricated and then electropolished (although as furtherdescribed, other wire profile reduction means are contemplated so as toproduce a different wire profile from the initial wire profile).Furthermore, it is assumed only for these next equations that the x andy values are identical, such that the X_(pre) and Y_(pre)values=X_(post) and Y_(post) respectively, wherein “pre” and “post”refer to pre-wire reduction and post-wire reduction. Making theseassumptions, Equation 1 simplifies to K=EI (hereafter “Equation 2”). Thesecond moment of inertia (for a circular cross-section) is defined by

$I = \frac{\pi \; D^{4}}{64}$

(hereafter “Equation 3”), where D=diameter of circular cross-section(m). Consequently, Equation 2 can be rewritten as

$K = \frac{E\; \pi \; D^{4}}{64}$

(hereafter “Equation 4”). Eliminating the constants in this equation,based on the assumptions cited above, the flexural stiffness is dictatedby D⁴. Thus, K∝D⁴ (hereafter “Equation 5”). Therefore a small change indiameter will have a large change in flexural stiffness.

The one or more wires comprising stent embodiments and equivalentsthereto are not limited to having a circular cross-sectional profile;other profiles are contemplated, including but not limited to, arectangular cross-section profile, square cross-sectional profile, ovalcross-sectional profile, triangular cross-section profile, an irregular(or non-uniform) cross-sectional profile, or some combination thereof.Accordingly, as used herein, a “profile” of the one or more wires may beany means of defining a diameter, length, width, height, or othermeasurement of a wire, such as is appropriate for the specific shape ofthe wire whether it be a circle, oval, rectangle, square, or othershape. Thus, although some embodiments illustrate a reduced wirediameter, the embodiments and methods are not limited to circularcross-sectional profile wires; instead, they include, but are notlimited to, one or more wires having any profile shape whether thatcross-sectional length, height, width, or other portion be describedusing a term other than “diameter.” Reducing the profile of the wiresuch that it is different from its initial wire profile may be achievedthrough numerous means, including but not limited to, reducing thediameter of a round wire and/or reducing the cross section of a flatwire or changing the shape of the wire. For example, it is contemplatedthat the shape of round wire may be altered into more rectangular shapeor other desired shape. A change of the wire profile may be achieved byelectropolishing, immersion into an acid, sanding/grinding, or somecombination thereof.

Accordingly, because the diameter of wire first portion 106 has beenchanged, the radial force is also reduced. However because stent body102 maintains its initial wire diameter, the radial force in thatportion is not reduced. Accordingly, reduced wire diameter stent 100performs like known wire stents but will likely reduce the incidence oftissue perforation caused by typical flanges and/or crowns perforatingtissue due to the typically high radial force exerted therefrom.

FIG. 1C illustrates a front cross-sectional view of an exemplaryproximal end 100 aa of a stent prior to wire profile reduction, and FIG.1D illustrates a front cross-sectional view of exemplary proximal end100 a of a stent after wire diameter reduction.

Referring to FIGS. 1C-1D, wires remain situated within the same plane Pbefore wire diameter reduction (illustrated in FIG. 1C) and after wirediameter reduction (illustrated in FIG. 1D). Moreover, as compared withproximal portion 100 aa (illustrated in FIG. 1C), the wire tension(illustrated in FIG. 1D) is reduced thereby resulting in a more flexibleproximal portion 100 a (illustrated in FIG. 1D) than proximal portion100 aa (illustrated in FIG. 1C).

FIG. 2 illustrates a side view of exemplary reduced wire diameter stent200 having proximal portion 200 a, distal portion 200 b, and a generallycylindrical tubular shaped stent body 202 having lumen 204 extendingthroughout. FIG. 2A illustrates a side view of exemplary stent wirecrown portion 203 a prior to wire diameter reduction, and FIG. 2Billustrates a side view of stent wire crown portion 203 after wirediameter reduction at the view 2B illustrated in FIG. 2. Referring toFIGS. 2-2B, at proximal portion 200 a and distal portion 200 b of stent200 are flanges 205 terminating in crowns 203. Stent 200 comprises asingle wire wound in a helical pattern; other embodiments of wire stentsare contemplated, including but not limited to, those fabricated fromtwo or more wires having helical or other configurations. After stent200 is fabricated, the diameter of wire first portion 206 is reduced bya first reduction amount, and the diameter of wire second portion 208 isreduced by a second reduction amount. For example, the diameter of wirefirst portion 206 is reduced by about 50%, and the diameter of wiresecond portion 208 is reduced by about 30%. Other reduction amounts arecontemplated. Because wire first portion 206 and wire second portion 208are reduced diameter wires, proximal portion 200 a and distal portion200 b of stent 200 are more flexible and less traumatic to tissue, andthus, less likely to perforate tissue. Accordingly, because the diameterof wire first portion 206 has been reduced by an amount greater thanwire second portion 208, the radial force at wire first portion 206 isless than at wire second portion 208, and is less than at stent body202. Because stent body 202 maintains its initial wire diameter, theradial force in that portion is not reduced. Accordingly, reduced wirediameter stent 200 performs like known wire stents but will likelyreduce the incidence of tissue perforation caused by typical flangesand/or crowns perforating tissue due to the typically high radial forceexerted therefrom.

FIG. 3 illustrates a side view of exemplary reduced wire diameter stent300 having proximal portion 300 a, distal portion 300 b, and a generallycylindrical tubular shaped stent body 302 having lumen 304 extendingthroughout. At proximal portion 300 a and distal portion 300 b of stent300 are flanges 305 terminating in crowns 303. Stent 300 comprises asingle wire wound in a helical pattern; other embodiments of wire stentsare contemplated, including but not limited to, those fabricated fromtwo or more wires having helical or other configurations. After stent300 is fabricated, the diameter of wire first portion 306 is reduced bya first reduction amount, and the diameter of wire second portion 308 isreduced by a second reduction amount. For example, the diameter of wirefirst portion 306 is reduced by about 50%, and the diameter of wiresecond portion 308 is reduced by about 30%. The reductions in diametersfor each portion may be the same or different, and other reductionamounts are contemplated. Because wire first portion 306 and wire secondportion 308 are reduced diameter wires, they are more flexible and lesstraumatic to tissue. Since a portion of stent body 302 maintains itsinitial wire diameter, the radial force in that portion is not reduced.Accordingly, reduced wire diameter stent 300 performs like known wirestents but will likely reduce the incidence of tissue perforation causedby typical flanges and/or crowns perforating tissue due to the typicallyhigh radial force exerted therefrom and by permitting body portion ofstent to be more flexible at wire second portion 308.

FIG. 4 illustrates a side view of exemplary reduced wire diameter stent400 having proximal portion 400 a, distal portion 400 b, and a generallycylindrical tubular shaped stent body 402 having lumen 404 extendingthroughout. At proximal portion 400 a and distal portion 400 b of stent400 are flanges 405 terminating in crowns 403. Stent 400 comprises asingle wire wound in a helical pattern; other embodiments of wire stentsare contemplated, including but not limited to, those fabricated fromtwo or more wires having helical or other configurations. After stent400 is fabricated, the diameter of wire first portion 406 is reduced bya first reduction amount, the diameter of wire second portion 408 isreduced by a second reduction amount, and the diameter of wire thirdportion 410 is reduced by a third reduction amount. For example, thediameter of wire first portion 406 is reduced by about 50%, the diameterof wire second portion 408 is reduced by about 30%, and the diameter ofwire third portion 410 is reduced by about 10%. The reductions indiameters for each portion may be the same or different, and otherreduction amounts are contemplated. Because wire first portion 406, wiresecond portion 408, and wire third portion 410 are reduced diameterwires, they are more flexible and less traumatic to tissue. Because aportion of stent body 402 maintains its initial wire diameter, theradial force in that portion is not reduced. Accordingly, reduced wirediameter stent 400 performs like known wire stents but will likelyreduce the incidence of tissue perforation caused by typical flangesand/or crowns perforating tissue due to the typically high radial forceexerted therefrom and by permitting body portion of stent to be moreflexible at wire third portion 410.

FIG. 5 illustrates exemplary method of manufacturing a reduced wireprofile stent 500, such as those illustrated in FIGS. 1-4. At block 502,a wire stent is fabricated. At block 504, a wire profile reductionsolution is mixed and is preferably made to an ideal temperature. Atblock 506, all or a portion of the stent is bathed in the solution whilebeing electropolished to the desired wire profile by applying anelectropolishing voltage to the wire profile reduction solution. Atblock 508, the stent is rinsed of the wire profile reduction solution.It is contemplated that an electropolishing voltage need not be applied,such as in the case of, for example, bathing stent in certain acidbaths.

FIG. 6 illustrates exemplary method of manufacturing a reduced wireprofile stent 600, such as those illustrated in FIGS. 1-4. At block 602,a wire stent is fabricated. At block 604, a wire profile reductionsolution of 62 ml perchloric acid, 700 ml ethanol, 100 ml butylcellusolve, and 137 ml distilled water is mixed and brought to roomtemperature. At block 606, all or a portion of the stent is bathed inthe solution while being electropolished using 6 volts for 1-3 minutessuch that the wire profile is reduced to the desired amount. Using thismethod, a typical stent's wire diameter having a circularcross-sectional profile (other profile configurations are contemplated)is reduced at a rate of about 0.0003 inches per minute.

At block 608, the stent is then rinsed of the wire profile reductionsolution by, for example, rinsing the stent in deionized water for aboutone minute. The stent is then neutralized in a mild basic solution,including but not limited to, aqueous sodium bi-carbonate, ammoniumhydroxide, or sodium hydroxide, for about 1-3 minutes. Thereafter, thestent is rinsed in deionized water for about one minute. It is preferredthat rinsing of the stent occurs using ultrasonic means and be done atroom temperature. Other rinsing materials, agents, and methods arecontemplated. Optionally, a coating or membrane can be applied to all ora portion of the stent.

Additional means and methods for reducing the wire profile of a stent orportion thereof such that the wire profile is different from its initialwire profile are illustrated in Table 1, below, such that the wireprofile reduction solution is mixed and brought to a preferredtemperature, and all or a portion of the stent is bathed and/orelectropolished until the wire profile is reduced to a certain shape,measurement, or by a certain percentage. The wire profile reductionsolution is then rinsed from the stent, by for example, rinsing thestent in deionized water for about one minute. The stent is thenneutralized in a mild basic solution, including but not limited to,aqueous sodium bi-carbonate, ammonium hydroxide, or sodium hydroxide,for about 1-3 minutes. Thereafter, the stent is rinsed in deionizedwater for about one minute. It is preferred that rinsing of the stentoccurs using ultrasonic means and be done at room temperature. Otherrinsing materials, agents, and methods are contemplated

The wire diameter reduction rates illustrated in FIG. 5 and Table 1assume a round wire stent fabricated from nitinol, but other materialsare contemplated which may alter the wire diameter reduction rate.Moreover, other wire profile reduction solutions are contemplated,including those for use with materials other than nitinol. The wireprofile reduction solutions contemplated are not limited to thoseillustrated in FIG. 5 and Table 1. For example, if the stent comprisesferrous shape memory alloys, then it is preferred, although notrequired, that the wire profile reduction solution comprise a mixture ofsulfuric—phosphoric acids, such as Electro-Glo™ (available fromElectro-Glo Distribution Inc., LaSalle, Ill.).

TABLE 1 Approximate Approximate Wire Diameter Approximate Duration ofReduction Wire Profile Reduction Solution Electropolishing Rate SolutionTemperature Bath (Inches/Min) 60 ml perchloric acid, Room 6 V for about1-3 About 0.0003. 590 ml methanol, and temperature. minutes. 350 mlbutyl cellusolve. 21 ml perchloric acid Room 6 V for about 1-3 About0.0003. (70%) and 79 ml acetic temperature. minutes. acid. 6 mlperchloric acid Room 6 V for about 1-3 About 0.0003. (70%) and 94 mlacetic temperature. minutes. acid. Pickle stent for 6 Room 20 V 0.15amps for About 0.0003. minutes in 2 ml temperature. about 1.5-2hydrofluoric acid and 40 ml minutes. nitric acid, and then bathe stentin 5 ml perchloric acid (70%) and 100 ml acetic acid. 30 ml nitric acid,10 ml Room 6 V for about 3-5 About 0.0005. sulphuric acid, 10 mltemperature. minutes. orthophosphoric acid, and 50 ml glacial aceticacid. 10 ml nitric acid, 5 ml Room 6 V for about 3-5 About 0.0005.acetic acid, and 85 ml temperature. minutes. distilled water. 50 mlnitric acid and 50 ml Room 6 V for about 3-5 About 0.0005. acetic acid.temperature. minutes. 33 ml nitric acid and 67 ml Cool solution 5.5 Vwith 0.1 A/cm² About 0.0003. methanol. to −30° Celsius. for about 3-5minutes. 30 ml nitric acid and 70 ml Cool solution 15 V for about 1About 0.0003. methanol. to −30° Celsius. minute. 0.01-1 gram chromiumRoom 6 V for about 3-5 About 0.0005. trioxide and 100 ml temperature.minutes. hydrochloric acid. 10 ml hydrofluoric acid, Room 6 V for about1-3 About 0.0003. 25 ml nitric acid, and temperature. minutes. 150 mldistilled water. 5 ml hydrofluoric acid, Room 6 V for about 1-3 About0.0005. 10 ml nitric acid, and temperature. minutes. 100 ml glycerin.

Care is to be taken when using any of the wire profile reductionsolutions, especially when using the wire profile reduction solutionscontaining acid, so as not to burn oneself or unintended portions of thestent. Wire profile reduction solutions not containing perchloric acidor hydrofluoric acid are generally less aggressive than those containingperchloric acid or hydrofluoric acid, but such solutions generallyreduce the wire diameter at a slower rate.

In some embodiments, only the end portions of the stent are eachsubjected to the wire profile reduction electropolishing bath. Forexample, as illustrated in FIG. 1, wire first portions 106 are eachsubjected to the wire profile reduction electropolishing bath to reducethe wire diameters by about 50%.

In some embodiments, one or more portions of the stent will be subjectedto one or more wire profile reduction electropolishing baths until thedesired reduced wire diameters are achieved. For example, as illustratedin FIG. 2, wire first portion 206 and wire second portion 208 aresubjected to the wire profile reduction electropolishing bath to reducethe wire diameter by about 30%. Thereafter, wire first portion 206 isfurther subjected to the wire profile reduction electropolishing bath tofurther reduce its wire diameter by about another 20%, such that wirefirst portion 206 has a final reduced wire diameter of about 50% fromthe initial wire diameter.

In some embodiments, a portion of the stent can be masked such that onlycertain portions of the stent are subjected to the wire profilereduction electropolishing bath at certain times. For example, asillustrated in FIG. 3, the portion of stent not to have a reduced wirediameter is masked while stent 300 is subjected to the wire profilereduction electropolishing bath until the diameter of wire first portion306 and wire second portion 308 are reduced by about 30%. Thereafter,all but wire first portion 306 is masked while stent 300 is subjected tothe wire profile reduction electropolishing bath until the diameter ofwire first portion 306 is reduced by about 20% to a total of about a 50%reduction from the initial wire diameter.

For example, as illustrated in FIG. 4, all but wire third portion 410 ismasked while stent 400 is subjected to the wire profile reductionelectropolishing bath until the diameter of wire third portion 410 isreduced by about 10%. Thereafter, all but wire second portion 408 ismasked while stent 400 is subjected to the wire profile reductionelectropolishing bath until the diameter of wire second portion 408 isreduced by about 30%. Thereafter, all but wire first portion 406 ismasked while stent 400 is subjected to the wire profile reductionelectropolishing bath until the diameter of wire first portion 406 isreduced by about 50%.

In some embodiments, stents and equivalents thereof have portions of awire outer surface or wire inner surface masked such that an irregularcross-section profile is created and/or the shape of the wire is alteredwhen subjected to the wire profile reduction electropolishing bath.

In some embodiments, two or more stents may be subjected to the wireprofile reduction electropolishing bath simultaneously to increase thespeed at which reduced wire profile stents may be manufactured. In someembodiments, the wire profile reduction solution amount will beincreased, preferably maintaining the ratio of each portion of thesolution (e.g., doubling, tripling, etc.), to accommodate two or morestents to be subjected to the wire profile reduction electropolishingbath. In some embodiments, the amount of time two or more stents aresubjected to the wire profile reduction electropolishing bath will bealtered, such as by increasing the exposure time, so as to accommodatetwo or more stents to be bathed simultaneously.

Other wire profile reduction means such that the wire profile isdifferent from its initial wire profile are contemplated in addition touse of a wire profile reduction electropolishing bath. Such means may beused separate or in conjunction with one another. For example, wireprofile reduction means include, but are not limited to, subjecting oneor more wires or portions thereof to a wire profile reductionelectropolishing bath, swaging one or more wires or portions thereof,crimping one or more wires or portions thereof, grinding one or morewires or portions thereof, and bathing one or more wires or portionsthereof in acid or other chemical(s) such that the one or more profilesof the wires or portions thereof is reduced or the wire configuration isotherwise altered such that the wire is more flexible and exhibits areduced moment of inertia.

As can be seen, embodiments of reduced wire profile stents may have oneor more portions of its body and/or flanges reduced by one or more wireprofile reduction amounts. Although FIG. 1, for example, illustrateswire first portions 106 having reduced wire diameters on both flanges105, it is contemplated that only a single portion of stent 100 includea reduced profile wire. In other words, the reduced profile wire portionneed not be included on both the proximal and distal portions of thestent and the resulting stent need not be symmetrical.

In some embodiments, only the proximal portion (or portions thereof) ofthe stent will have a reduced profile wire. In some embodiments, onlythe distal portion (or portions thereof) of the stent will have areduced profile wire. In some embodiments, only the middle stent bodyportion (or portions thereof) of the stent will have a reduced profilewire. In some embodiments, the stent will have a combination of reducedprofile wire portions on various portions of the stent. In someembodiments, the reduced profile wire portions will be adjacent to eachother. In some embodiments, the reduced profile wire portions will beseparate from each other.

In some embodiments, the reduced profile wire portions will be reducedby the same amount. In some embodiments, the reduced profile wireportions will be reduced by different amounts. In some embodiments, thereduced profile wire portions will abruptly change from one profile sizeor configuration to another.

In some embodiments, the reduced profile wire portions will graduallychange from one profile size or configuration to another, such as in atapered reduction rate, as illustrated in FIG. 2C, wherein crown portion203 b has a reduced tapered wire diameter. Still referring to FIG. 2C,reduction angle A preferably is a shallow angle of about 0.1 degrees,0.01-2 degrees, but other angles are contemplated depending upon thelength of the taper and the desired wire profile. Means for achieving atapered reduced wire profile configuration include, but are not limitedto, a controlled slow withdrawal from the wire profile reductionelectropolishing bath and/or other wire profile reduction means.

In some embodiments, the wire profile will be reduced by about 1%-50%.In some embodiments, the wire profile will be reduced by more than 50%,such as 70%, taking care not to reduce the wire profile by too high ofan amount such that the wire will fail due to fatigue. For example, insome embodiments the wire profile will be reduced by from about 10% toabout 75%. In other embodiments, the wire profile will be reduced byabout 10-25%, about 25-40%, about 40-60%, or about 60-75%. In stillother embodiments, the wire profile will be reduced by about 50%.

In some embodiments, the voltage applied to a wire profile reductionelectropolishing bath will be the same or different from the voltageapplied to other wire profile reduction electropolishing baths to reducethe wire diameter of one or more portions of a stent. In someembodiments, the wire profile reduction solutions used to reduce thewire diameter of one or more portions of the stent will be the same ordifferent. In some embodiments, the amount of time portions of a stentare subjected to a wire profile reduction electropolishing bath will bethe same or different.

In some embodiments, a stent is covered with a membrane. The membranecovering may be applied to a stent by any suitable method as is known inthe art. For example, the membrane may be applied by spraying, dipping,painting, brushing, or padding. Generally, the membrane covering orcoating has a thickness ranging from about 0.0025 mm to about 2.5 mm.The thickness of the membrane may be selected, for example, bycontrolling the number of dips or passes made during the applicationprocess. In one exemplary embodiment, a braided stent may be dipped insilicone liquid, removed, and thereafter cured. Preferably, the coatingextends over the abluminal and luminal surfaces of the filaments, andalso resides in the cells or interstices defined by the filament braidpattern. In certain embodiments, the coating may be selectively appliedto the luminal or abluminal surfaces of the stent structure such thatthe coating residing within the cells is biased to the luminal orabluminal surface of the stent structure.

In some embodiments, after the membrane has been applied to the stentstructure, “soft cells” may be created by manually removing a covering,such as silicone, from the selected cells with an appropriate tool. Forexample, devices such as needles and forceps may be used to removemembrane material from selected cells to create a desired pattern ofsoft cells. In an alternative embodiment, the soft cells in the stentpattern may fabricated by covering or shielding certain cells prior toapplication of the membrane coating. For example a segment of shrinkwrap comprising polytetrafluoroethylene may be applied to acircumferential row of cells by placing a piece of the material at thedesired location and thereafter heat shrinking in place. With theselected cells shielded, the membrane material may be applied and cured,and the shrink wrap thereafter removed. This procedure may minimize oreliminate the need for manual removal of silicone from selected cells.

In some embodiments, a bioactive agent may be applied, for example, byspraying, dipping, pouring, pumping, brushing, wiping, vacuumdeposition, vapor deposition, plasma deposition, electrostaticdeposition, ultrasonic deposition, epitaxial growth, electrochemicaldeposition or any other method known to the skilled artisan.

In some embodiments, prior to applying the membrane, a stent may bepolished, cleaned, and/or primed as is known in the art. A stent may befurther polished, for example, with an abrasive or by electropolishing.A stent may be cleaned by inserting the stent into various solvents,degreasers, and cleansers to remove any debris, residues, or unwantedmaterials from the stent surfaces. Optionally, a primer coating may beapplied to the stent prior to application of the membrane covering orcoating. Preferably, the primer coating is dried to eliminate or removeany volatile components. Excess liquid may be blown off prior to dryingthe primer coating, which may be done at room temperature or at elevatedtemperatures under dry nitrogen or other suitable environments includingan environment of reduced pressure.

In some embodiments, a stent may include a single flange, twoasymmetrically shaped flanges, or may entirely lack flanges and insteadhave a uniform or substantially uniform lumen diameter along the entirelength of the stent. In some embodiments, a stent may comprise aproximal tube portion, a distal tube portion, a central tube portiondisposed between the proximal tube portion and the distal tube portion,such that the stent forms a continuous structure having a substantiallyuniform inner diameter and outer diameter throughout. A stent mayinclude a uniform lumen diameter along the length of the stent butinclude slightly flared proximal and/or distal ends. The central bodyportion may smoothly transition to a flange or flare, or alternatively,may progressively step up in lumen diameter to a flange or flare.

Generally, a stent may be implanted in a vessel (e.g., esophagus,duodenum, colon, trachea, or the like) such that the central bodyportion engages a diseased area and the flanges or ends engage healthytissue adjacent the diseased area. Preferably, the flanges areconfigured to anchor the stent at the site of implantation, therebyreducing the incidence of antegrade and retrograde migration.Preferably, the flanges are sized and shaped to accommodate the vesselor organ of implantation. For example, stents destined for loweresophageal implantation may have differently shaped and sized flangescompared to a stent designed for upper esophageal implantation. Further,the flanges may be atraumatically shaped to reduce incidence of tissueperforation and overgrowth. For example, the absolute ends of theflanges may curve or bend inward toward the stent lumen to minimizetissue damage at or near the stent ends. In certain embodiments, a stentmay include other design elements configured to secure the stent at thesite of implantation. For example, in certain embodiments, a stent mayinclude anchors, hooks, or barbs that will anchor the stent to theinternal wall of the targeted body lumen. In other embodiments, thestent may be sutured to the site of implantation at one or more portionsof the stent structure.

In some embodiments, a stent may include one or more componentsconfigured to aid in visualization and/or adjustment of the stent duringimplantation, repositioning, or retrieval. For example, a stent mayinclude one or more radiopaque markers configured to provide forfluoroscopic visualization for accurate deployment and positioning.Radiopaque markers may be affixed (e.g., by welding, gluing, suturing,or the like) at or near the ends of the stent at a cross point of thewire. In some embodiments, a stent may include four radiopaque markerswith two markers affixed to a first flange and two to a second flange.Optionally, radiopacity may be added to a stent through covering (alsoreferred to as coating) processes such as sputtering, plating, orco-drawing gold or similar heavy metals onto the stent. Radiopacity mayalso be included by alloy addition. Radiopaque materials and markers maybe comprised of any suitable biocompatible materials, such as tungsten,tantalum, molybdenum, platinum, gold, zirconium oxide, barium salt,bismuth salt, hafnium, and/or bismuth subcarbonate. Additional methodsare contemplated, including but not limited to, use of palladium or anitinol wire with a platinum core, such as the DFT® wire available fromFort Wayne Metals, Fort Wayne, Ind.

It is preferable that radiopaque markers be added after the wire profilereduction electropolishing bath occurs so as to prevent damaging theradiopaque markers, if, for example, in the form of radiopaque bands.For example, radiopaque bands may be crimped onto the stent after thewire profile reduction electropolishing bath. Alternatively, radiopaquemarkers may be pushed out from the area subjected to the wire profilereduction electropolishing bath. Alternately, radiopaque markers may bemasked from the area subjected to the wire profile reductionelectropolishing bath.

In some embodiments, a stent may include one or more loops, lassos, orsutures on the stent structure to facilitate repositioning or removal ofthe stent during or after implantation. For example, a stent may includea loop at or near the proximal end of the stent. The loop material maycircumscribe the flange and in certain embodiments may be wound throughthe absolute end cells to affix the loop to the stent. The loop maycomprise any appropriate biocompatible materials, such as for example,stainless steel, suture materials or other polymeric materials such aspolyethylene, ultra-high molecular weight polyethylene, polyester,nylon, or the like. Optionally, the lasso may be coated with a material,such as polytetrafluoroethylene, to reduce frictional interactions ofthe lasso with surrounding tissue.

In some embodiments, stents may be self-expanding, mechanicallyexpandable, or a combination thereof. Self-expanding stents may beself-expanding under their inherent resilience or may be heat activatedwherein the stent self-expands upon reaching a predetermined temperatureor range of temperatures. One advantage of self-expanding stents is thattraumas from external sources or natural changes in the shape of a bodylumen do not permanently deform the stent. Thus, self-expanding stentsare often used in vessels that are subject to changes in shape and/orchanges in position, such as those of the peripheral andgastrointestinal systems. Peripheral vessels regularly change shape asthe vessels experience trauma from external sources (e.g, impacts toarms, legs, etc.); and many gastrointestinal vessels naturally changeshape as peristaltic motion advances food through the digestive tract.

One common procedure for implanting a self-expanding stent involves atwo-step process. First, if necessary, the diseased vessel may bedilated with a balloon or other device. The stent may be loaded within asheath that retains the stent in a compressed state for delivery to thetargeted vessel. The stent may then be guided to the target anatomy viaa delivery catheter and thereafter released by retracting or removingthe retaining sheath. Once released from the sheath, the stent mayradially expand until it contacts and presses against the vessel wall.In some procedures, self-expanding stents may be delivered with theassistance of an endoscope and/or a fluoroscope. An endoscope providesvisualization of the lumen as well as working channels through whichdevices and instruments may be delivered to the site of implantation. Afluoroscope also provides visualization of the patient anatomy to aid inplacement of an implantable device, particularly in the gastrointestinalsystem.

Stents according to the present disclosure may be formed by any suitablemethod as is known in the art. In certain embodiments, stents may befabricated by braiding, weaving, knitting, crocheting, welding,suturing, or otherwise machining together one or more filaments or wiresinto a tubular frame. Such stents may be referred to as braided, woven,or mesh stents. A braided stent may be fabricated by, for example, useof a braiding mandrel having specifically designed features (e.g.,grooves and detents) for creating such a stent. A variety of braidingpatterns are possible, such as for example, one-under and one-overpatterns or two-under and two-over patterns. The filaments or wires maybe of various cross-sectional shapes. For example, the filaments orwires may be flat in shape or may have a circular-shaped cross-section.The filaments or wires may have any suitable initial diameter, such asfor example, from about 0.10 to about 0.30 mm.

In some embodiments, stents may be formed from metallic or polymericsheets or tubular blanks. For example, a stent framework comprising aselected pattern of struts defining a plurality of cells or intersticesmay be fabricated by subjecting a metallic or polymeric sheet or tubularblank to laser cutting, chemical etching, high-pressure water etching,mechanical cutting, cold stamping, and/or electro discharge machining.After obtaining a sheet of cut, etched or machined material with theappropriate strut pattern, the sheet may be rolled into a tubular shapeto form the stent framework. The stent framework may also be machinedfrom a tubular blank, thereby eliminating the need for a rolling step.

In some embodiments, a stent may be made from any suitable biocompatiblematerial(s). For example, a stent may include materials such as shapememory alloys, stainless steel, nitinol, MP35N, gold, tantalum, platinumor platinum iridium, niobium, tungsten, Iconel® (available from SpecialMetals Corporation, Huntington, W. Va.), ceramic, nickel, titanium,stainless steel/titanium composite, cobalt, chromium, cobalt/chromiumalloys, magnesium, aluminum, or other biocompatible metals and orcomposites or alloys. Examples of other materials that may be used toform stents include carbon or carbon fiber; cellulose acetate, cellulosenitrate, silicone, polyethylene terephthalate, polyurethane, polyamide,polyester, polyorthoester, polyanhydride, polyether sulfone,polycarbonate, polypropylene, ultra high molecular weight polyethylene,polytetrafluoroethylene, or another biocompatible polymeric material, ormixtures or copolymers of these; polylactic acid, polyglycolic acid orcopolymers thereof; a polyanhydride, polycaprolactone,polyhydroxybutyrate valerate or another biodegradable polymer, ormixtures or copolymers of these; a protein, an extracellular matrixcomponent, collagen, fibrin, or another biologic agent; or a suitablemixture of any of these.

In some embodiments, a stent may be fabricated to any suitabledimensions. A stent having a particular length and diameter may beselected based on the targeted vessel. For example, a stent designed foresophageal implantation may have a length ranging from about 5 cm toabout 15 cm and a body diameter of about 15 mm to about 25 mm.Optionally, an esophageal stent may include one or more flanges orflares of about 10 mm to about 25 mm in length and about 20 mm to about30 mm in diameter. For example, a stent designed for colon implantationmay have a length ranging from about 5 cm to about 15 cm and a bodydiameter of about 20 mm to about 25 mm. Optionally, a colonic stent mayinclude one or more flanges having a diameter of about 25 mm to about 35mm.

A stent according to the present disclosure may be delivered to a bodylumen using various techniques. Generally, under the aid of endoscopicand/or fluoroscopic visualization a delivery device containing the stentis advanced into the vicinity of the target anatomy. The targeted lumenmay be predilated with a balloon catheter or other dilation device, ifnecessary. Preferably, the stent is delivered in a compressed state in alow profile delivery device. This approach may reduce the risk of tissueperforations during delivery. Once the delivery device is in place, thestent may be released from the retaining sheath or the like. In onepreferred embodiment, a stent may be delivered with a controlled releasesystem (e.g., Evolution™ Controlled-Release Stent, Cook Endoscopy Inc.,Winston-Salem, N.C.). A controlled release device permits the physicianto slowly release the stent from the retaining sheath and in someinstances, recapture the stent to allow for repositioning. Afterimplantation, the delivery device and any other devices (e.g., wireguides, catheters, etc.) may be removed.

From the foregoing, the discovery of methods and apparatuses of stentswith likely reduced rates of tissue perforation are achieved by variousmethods and apparatus, including but not limited to, reducing theprofile one or more portions of a stent using a wire profile reductionelectropolishing bath and/or other wire profile reduction means. It canbe seen that the embodiments illustrated and equivalents thereof as wellas the methods of manufacturer may utilize machines or other resources,such as human beings, thereby reducing the time, labor, and resourcesrequired to manufacturer the embodiments. Indeed, the discovery is notlimited to the embodiments illustrated herein, and the principles andmethods illustrated herein may be applied and configured to any stentand equivalents.

Those of skill in the art will appreciate that embodiments not expresslyillustrated herein may be practiced within the scope of the presentdiscovery, including that features described herein for differentembodiments may be combined with each other and/or with currently-knownor future-developed technologies while remaining within the scope of theclaims presented here. It is therefore intended that the foregoingdetailed description be regarded as illustrative rather than limiting.It is understood that the following claims, including all equivalents,are intended to define the spirit and scope of this discovery.Furthermore, the advantages described above are not necessarily the onlyadvantages of the discovery, and it is not necessarily expected that allof the described advantages will be achieved with every embodiment ofthe discovery.

What is claimed is:
 1. A stent comprising: a wire configured into atubular body comprising a proximal tube portion, a distal tube portion,a central tube portion disposed between the proximal tube portion andthe distal tube portion, and a lumen extending between the proximal tubeportion and the distal tube portion; wherein the wire comprises a firstprofile and a second profile, wherein the second profile is differentfrom the first profile.
 2. The stent of claim 1, wherein the secondprofile is about 10% to about 75% smaller than the first profile.
 3. Thestent of claim 1, wherein the wire further comprises a third profile,wherein the third profile is less than each of the first profile and thesecond profile.
 4. The stent of claim 1, wherein at least one of theproximal tube portion or distal tube portion comprises the secondprofile.
 5. The stent of claim 1, wherein the proximal tube portioncomprises the second profile and the distal tube portion comprises thesecond profile.
 6. The stent of claim 1, wherein the proximal tubeportion comprises the first profile and the second profile, wherein thedistal tube portion comprises the first profile and the second profile,and wherein the central tube portion comprises a third profile largerthan each of the first profile and the second profile.
 7. The stent ofclaim 1, wherein at least one of the proximal tube portion or distaltube portion comprises a flange.
 8. A method of manufacturing a reducedwire profile stent comprising: bathing a first portion of a wire stentin a first wire profile reduction solution; and applying a firstelectropolishing voltage to the first wire profile reduction solutionbath to reduce the profile of the first portion of the wire stent. 9.The method of claim 8, further comprising: rinsing the wire stent of thefirst wire profile reduction solution.
 10. The method of claim 9,wherein the rinsing the wire stent of the first wire profile reductionsolution further comprises rinsing the wire stent with deionized water.11. The method of claim 8, wherein a portion of the wire stent is maskedwhile bathing a first portion of the wire stent in the first wireprofile reduction solution.
 12. The method of claim 8, furthercomprising: bathing a second portion of the wire stent in a second wireprofile reduction solution; and applying a second electropolishingvoltage to the second wire profile reduction solution bath to reduce theprofile of the second portion of the wire stent; wherein the secondportion of the wire stent is the same or different from the firstportion of the wire stent, wherein the first wire profile reductionsolution is the same or different from the second wire profile reductionsolution, and wherein the first electropolishing voltage is the same ordifferent from the second electropolishing voltage.
 13. The method ofclaim 8, wherein the first wire profile reduction solution comprises atleast one of perchloric acid, ethanol, butyl cellusolve, water,methanol, acetic acid, hydrofluoric acid, nitric acid, sulphuric acid,orthophosphoric acid, glacial acetic acid, chromium trioxide,hydrochloric acid, and glycerin.
 14. The method of claim 8, wherein theapplying the first electropolishing voltage to the first wire profilereduction solution bath to reduce the profile of the first portion ofthe wire stent occurs for about 1-5 minutes.
 15. The method of claim 8,wherein the first electropolishing voltage is about 3-15 volts.
 16. Themethod of claim 8, further comprising bringing the first wire profilereduction solution to a temperature of at least one of about roomtemperature or about −30° Celsius.
 17. A method of manufacturing achanged profile wire stent comprising: subjecting a first portion of awire stent to a wire profile reduction means to change the profile ofthe first portion of the wire stent.
 18. The method of claim 17, whereinthe wire profile reduction means comprises a wire profile reductionelectropolishing bath comprising at least one of perchloric acid,ethanol, butyl cellusolve, water, methanol, acetic acid, hydrofluoricacid, nitric acid, sulphuric acid, orthophosphoric acid, glacial aceticacid, chromium trioxide, hydrochloric acid, and glycerin.
 19. The methodof claim 17, wherein the wire profile reduction means comprises at leastone of: subjecting one or more portions of the wire stent to a wireprofile reduction electropolishing bath, swaging one or more portions ofthe wire stent, crimping one or more portions of the wire stent,grinding one or more portions of the wire stent, or bathing one or moreportions of the wire stent in a chemical.
 20. The method of claim 18,wherein an electropolishing voltage applied to the wire profilereduction means is about 3-15 volts.